When you reopen the document, are you opening it in Adobe Reader or another application? When you open it the first time in Adobe Reader, where are you opening it from? Can you share the name of the application and email the document you are editing to email@example.com?
Some applications do not support viewing comments even though it is part of the ISO PDF standard. However, if you are opening it in Adobe Reader, we'd expect you to be able to view the comments. If it is not working, I'd like to troubleshoot the problem.
Thank you for your question.